1. Field of the Invention
The present invention relates generally to tubular structures and, particularly, to fuel filler tubes such as fuel filler tubes for delivering fuel from a fuel filler port to a fuel tank in an automobile and to a method for manufacturing such fuel filler tubular structures.
2. Technical Background and Related Art
Fuel filler tubes are tubular structures extending from a fuel filler port to a fuel storage tank in a vehicle and provide a conduit for delivering fuel from a nozzle designed to deliver fuel from fuel source such as a gas pump to the fuel storage tank. Fuel filler tubes have been constructed from a variety of materials such as metals and polymers in order to prevent permeation of fuel vapor into the atmosphere. Previously, metals, such as steel, were used in the manufacture of fuel filler tubes. Metal fuel filler tubes were effective in preventing initial permeation of fuel vapor, but were highly susceptible to corrosion which led to eventual permeation of fuel through corroded holes or cracks in the fuel filler tube. Polymeric materials are effective to overcome the corrosion problem, but they require multiple layers of specialized polymeric materials and complex formulations in order to reduce permeation of fuel vapor to an acceptable level. Recently, the expense of specialized polymeric materials due to the increasing cost of oil which is the main ingredient in producing polymeric materials, and the increased manufacturing cost of the complex blends and formulations of the polymeric materials, are causing the industry to reevaluate the use of polymeric materials and look to metallic materials such as steels having improved corrosion resistance for the manufacture of fuel filler tubes as well as other fluid and vapor tubes.
In the past, fuel filler tubes made of steel pipe have been coated with a chromium layer and then painted. However, such coated and painted steel fuel filler tubes are not always protected from corrosion, particularly in areas having a high salt environment such as coastal areas and where road salt is used in winter to remove ice from roadways. Additionally, corrosion can also occur inside the fuel filler tube when exposed to a corrosive atmosphere containing denatured gasoline or alcohol-based fuels. Examples of metallic tubes for various uses are found in the following U.S. patent application Publication and in the following U.S. patents:
U.S. Pat. Appln. No. 2005/0280259 A1 to Sausner, et al. describes a multilayer metallic high pressure conduit for a high pressure medium such as used in a fuel injection system in a motor vehicle. The multilayer conduit has a metallic inner layer, one or more metallic intermediate layers and a metallic outer layer. The layers forming the conduit are coaxially fitted into the pressed against one. Each of the inner layer, the one or more intermediate layers and the outer layer are formed of steel, preferably stainless steel, and all of the layers extend the longitudinal length of the conduit.
U.S. Pat. No. 7,048,019 B2 to Pacitto, Jr., et al. teaches a fuel filler assembly including a single layer fuel filler tube formed by cutting a length of tube stock which may be a metal or a polymer. One end of the tube is joined to a funnel insert and the opposite end is joined to a fuel tank. Preferably, the fuel filler tube includes an integrally formed nozzle receptor.
U.S. Pat. No. 6,851,455 B2 to Otsuka, et al. describes a single layer metallic fuel filler tube made of austenitic stainless steel having improved corrosion resistance.
U.S. Pat. No. 6,802,430 B2 to Tomimura, et al. describes a single layer metallic fuel filler tube made from ferritic stainless, which is coated with a corrosion-preventing material such as a cathodic paint or a plating of Al, Zn or Zn alloy containing one or more of Fe, Ni, Co, Mg, Cr, Sn and Al.
U.S. Pat. No. 6,668,455 B2 to Duvall, et al. describes a multi-layer tube having a metal inner tube having a Zn coating such as Zn plating, Zn—Ni alloys, Zn—Co alloys, Zn—Al alloys, and mixtures thereof, and a surface treatment coating bonded to the Zn layer. The Zn layer is a Zn/Al/rare earth alloy, phosphate, chromate or a mixture thereof. One or more polymeric layers form the outer surface of the tube. The invention is concerned with the removal of the one or more polymeric outer layers adjacent the sealing areas of the tube to prevent potential loss of assembly torque over the long term of a vehicle's life, which could occur if the relatively soft polymeric material should extrude out of the sealing area and fitting compression area after assembly.
U.S. Pat. No. 5,620,805 to Ogawa, et al. teaches a multilayer steel tube for boilers, etc. used in installations where fossil fuel or combustible refuse is burnt. The multilayer steel tube has a base steel layer and an inner liner and an outer liner, wherein the inner and outer liners provide corrosion resistance in an environment where fuel containing V, Na, S and Cl is burnt. The inner and outer layers comprise an alloy containing up to 0.05% C, 1.0-2.6% Si, 0.02-0.5% Mn, 20.0-28.0% Cr, 24-36% Ni, up to 4.0% Mo, up to 0.4% Nb, up to 0.05% Al, and the balance Fe.
U.S. Pat. Nos. 5,581,862; 5,390,808; and 5,253,773, all to Choma, et al., disclose a single rolled steel tube which includes a plurality of sections having varying diameters.
U.S. Pat. No. 5,553,640 to Ferenczy, et al. disclose a flat steel band having a copper alloy brazing layer fixedly attached to at least one side of the steel band. The steel band is helically wound and subsequently soldered to form a multilayer tube that is particularly useful for brake line in a motor vehicle.
U.S. Pat. No. 4,185,844 to Hubbard, et al. discloses a single layer aluminum fuel filler tube.
The emergence of new and better steels is one reason for the recent trend towards the use of metals, particularly steel, in the manufacture of fuel filler tubes. Metals such as anti-corrosive steel provide excellent barrier properties against hydrocarbon permeation. Metals also provide high structural integrity. However, there are still obstacles to be overcome in order to rely totally on metal fuel filler tubes. For example, in conventional metallic fuel filler tubes, the assembly typically requires a non-metallic joint in order to achieve a robust connection of the fuel filler tube to the fuel tank. Furthermore, the non-flexibility of metallic fuel filler tubes makes it difficult to employ such metallic fuel filler tubes in today's automotive vehicles because of reduced space constraints.
Accordingly, there is a need in the industry for a fuel filler tube which overcomes the above disadvantages.